1. Field of the Invention
The invention is directed to an apparatus for accurately metering and mixing two or more materials, commonly to initiate a polymerization reaction, and for collecting the resultant product in a selected one of a plurality of collection vessels.
2. Description of the Prior Art
Reaction injection molding ("RIM") is the injection into a mold of a mixture of two or more liquid reactants which rapidly react upon impingement or in a heated mold to form a polymer such as a polyurethane, a polyamide, a polyester, or the like. The reactants must be present in the mixture in the appropriate stoichiometric proportions and must be thoroughly mixed with one another to achieve the best results. RIM may also be used to blend reagents.
The reactants in RIM systems are impingement mixed. That is, two or more streams of liquid reactants are directed into collision in the mixing head of a RIM apparatus. The volume/time rates of flow of the reactants in their respective streams correspond with the appropriate stoichiometric ratios required for the reaction. The collision of the streams should be as direct as possible given the number of colliding streams. For two liquid reactants, jets are provided which typically direct streams in nearly headon collision.
Studies have indicated that thorough mixing is dependent upon achieving a sufficiently high Reynolds number for each impinging stream. The Reynolds number for any given stream is a dimensionless quantity and is a function of the fluid density, the average of velocity of the fluid stream, the hydraulic diameter of the jet through which the stream passes and the fluid's viscosity. The formula for determining Reynolds numbers appears elsewhere, for example, in U.S. Pat. No. 4,189,070 by Macosko et al, issued Feb. 19, 1980. For a given fluid, density and viscosity are a function of temperature and pressure. In a RIM apparatus, hydraulic diameter, the average velocity, and the temperature of the fluid streams may be adjusted to achieve an appropriate Reynolds number.
Prior art devices have been primarily directed to an industrial setting. In an industrial setting, the devices have had hydraulic drive components available for driving reciprocating pistons in cylinders to attain the required high pressures. Few systems have been provided which are appropriate or are directed to experimentation with the compounds produced by reaction injection molding. Even the device of the Macosko et al patent, which is nominally directed to laboratory research, employs gas or hydraulic driven power to pressurize the reactants.
Prior art RIM machines have been large and relatively immobile. A need for a portable device, of low enough weight and small enough size to be readily moved and manipulated has not been met. Such a portable RIM device could be used for quality control and process development in both research and in industrial settings. A portable RIM device would be particularly amenable for use in microgravity environments, such as found on a space shuttle in orbit, for the manufacture of polymer materials with potentially novel and advantageous properties resulting from distinctive microstructures or molecular morphologies which may form in such an environment. A portable RIM apparatus should also be highly modular to allow it to work with a variety of reagents, e.g. particulate containing fluids.